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Astronomy. — "The nebulae considered in relation to the galactic 

 sj/stem." B}^ C. Easton. (Comiminicated by Piof. H. G. van dk 

 Sande Bakhuizen. 



If we consider the nebulae as forininm' part of oiii- galactic system 

 (comp. my previous paper "On the apparent dislribiilion of nebulae") 

 their distribution must be considered in connection with (hat of the 

 other classes of objects in this system. And then, speaking genei-ally, 

 we not only find a contrast between the ap[)arent distribution of the 

 stars (and clusters) and tiie nebulae, but also between the distribution 

 of the large dilTused nebulae (which, as far as we know, occur almost 

 exclusively in the region of the Milky Way) and that of the nebulae 

 proper; on the other hand it is probable that the galactic agglome- 

 ••ations for the greater })art consist of stars of the first spectral type. 



Stariiiig from the consideration that the nebular and the star-like 

 conditions are })hases in the development of matter and no invariable 

 final phases, it is obvious that as the distribution of the star-like 

 matter in some parts of the system differs from that in the others 



— which is accompanied by a different constitution of most of the 

 centers themselves, as appears from the spectral differences — so the 

 distribution and the constitution of the matter which exists in the 

 nebular condition will not be the same throughout the system. 



In the galactic region of the system we find a great number of 

 stai'-like objects pi'obably placed for the greater part at (relatively) 

 small distances from each other, mostly of the first spectral type. 

 In the "extra-galactic" i)ortions of the system we observe a smaller 

 number of suns, separated by vast distances and belonging for a 

 great part to the second spectral type. 



In the same way we find in and outside the galactic region proper 

 two forms of nebulae. In it are found the "green" nebulae with a 

 spectrum formed of lines, sometimes round and fairly well-defined 

 (planetary nebulae), but mostly extending over immense regions which 

 they cover as with a veil (large diffused nebulae). In the extra- 

 galactic regions we find the "white" nebulae with a continuous or 



— more probably — a mixed spectrum ; isolated and generally 

 widely separated objects, probably as a rule of a spiral form, and 

 certainly more condensed than those of the other kind. 



As little as we can sharply distinguish between star-like and 

 nebular objects, is the above mentioned disliuction intended as a 

 precise classification. But thus taken iu connection with the "galacto- 

 phily" of the "green" nebulae, the "galacto|)lioby" of the nebulae 

 proper does not appear as something exceptional; this principal 



